This invention relates to a device for generating a synchronous sound, which relates to a model railway engine.
With model railways it is desired to perceive a sound when an engine runs on the track. It is expressively demanded in connection therewith, that the sound relating to a moving engine shall be synchronous with the movement of the engine, and that the sound shall be adapted to the type of engine in question.
An extremely great number of large and complicated model railways exist today all over the world. Their owners, mostly clubs, demand also that the sound of the model engine should be adapted to the corresponding real engine. From the sound, it should be apparent, for example, whether a steam locomotive has an engine of single, double or triple cylinder type.
It is known previously to use electronic circuits for generating a sound which, for example, corresponds to the "puff-puff" sound of a steam engine. The conventional sound-generating units are intended to be located centrally in a model installation and to feed loudspeakers located in the room where the model railway is arranged. It is also known to emit the generated sound signals as an a-c voltage on the railway rails and to position a miniature loudspeaker in or at the engine in question, so that the sound is emitted from the engine.
It was found very difficult, however, to obtain a sound, which is synchronous with the engine speed, and a sound, of which the number of "puff-puff"s correspond to the mode of operation of the engine type in question.
The present invention offers a very simple device for overcoming the aforesaid difficulty.. The device according to the present invention generates a sound, which correctly corresponds to the real sound of and is synchronous with the speed of the engine.
The present invention, thus, relates to a device for generating a synchronous sound relating to an engine at model railways, comprising a first unit intended to generate by means of electronic circuits sound signals adapted to a certain engine, and to emit the generated sound signals to the engine via conductors, preferably the ones which supply the engine with operation voltage, and a second unit, which is located at the engine and preferably includes a loudspeaker, and which comprises a synchronization set capable to emit pulses in time with the rotation of the engine wheels and connected to said first unit via said conductors, thereby emitting the pulses to said first unit, and that said first unit is capable to emit an a-c voltage corresponding to an emitted pulse or pulses via said conductors to the loudspeaker when a pulse or a number of pulses are emitted from the synchronization set.
The invention is characterized in that said synchronization set comprises a light diode, a phototransistor or a corresponding element and includes marks on the inside of the engine wheels where the light diode and, respectively, phototransistor are located in order to light the inside of the wheel and, respectively, receive light reflected from the inside.